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CHEMICAL ENGINEERING (188 journals)                     

Showing 1 - 0 of 0 Journals sorted alphabetically
AATCC Journal of Research     Full-text available via subscription   (Followers: 3)
ACS Sustainable Chemistry & Engineering     Hybrid Journal  
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials     Hybrid Journal   (Followers: 5)
Acta Polymerica     Hybrid Journal   (Followers: 7)
Additives for Polymers     Full-text available via subscription   (Followers: 20)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 5)
Advanced Chemical Engineering Research     Open Access   (Followers: 12)
Advanced Powder Technology     Hybrid Journal   (Followers: 12)
Advances in Applied Ceramics     Hybrid Journal   (Followers: 4)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 22)
Advances in Chemical Engineering and Science     Open Access   (Followers: 33)
Advances in Polymer Technology     Hybrid Journal   (Followers: 12)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 6)
Annual Review of Analytical Chemistry     Full-text available via subscription   (Followers: 9)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 8)
Anti-Corrosion Methods and Materials     Hybrid Journal   (Followers: 6)
Applied Petrochemical Research     Open Access   (Followers: 2)
Asia-Pacific Journal of Chemical Engineering     Hybrid Journal   (Followers: 7)
Biochemical Engineering Journal     Hybrid Journal   (Followers: 13)
Biofuel Research Journal     Open Access   (Followers: 3)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 9)
Brazilian Journal of Chemical Engineering     Open Access   (Followers: 3)
Bulletin of Chemical Reaction Engineering & Catalysis     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 3)
Carbohydrate Polymers     Hybrid Journal   (Followers: 7)
Catalysts     Open Access   (Followers: 6)
ChemBioEng Reviews     Full-text available via subscription  
Chemical and Engineering News     Free   (Followers: 11)
Chemical and Materials Engineering     Open Access   (Followers: 3)
Chemical and Petroleum Engineering     Hybrid Journal   (Followers: 10)
Chemical and Process Engineering     Open Access   (Followers: 6)
Chemical and Process Engineering Research     Open Access   (Followers: 8)
Chemical Engineering & Technology     Hybrid Journal   (Followers: 31)
Chemical Engineering and Processing: Process Intensification     Hybrid Journal   (Followers: 17)
Chemical Engineering and Science     Open Access   (Followers: 6)
Chemical Engineering Communications     Hybrid Journal   (Followers: 11)
Chemical Engineering Journal     Hybrid Journal   (Followers: 22)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 20)
Chemical Engineering Research Bulletin     Open Access   (Followers: 2)
Chemical Engineering Science     Hybrid Journal   (Followers: 18)
Chemical Geology     Hybrid Journal   (Followers: 14)
Chemical Papers     Hybrid Journal   (Followers: 2)
Chemical Product and Process Modeling     Hybrid Journal   (Followers: 3)
Chemical Reviews     Full-text available via subscription   (Followers: 141)
Chemical Society Reviews     Full-text available via subscription   (Followers: 39)
Chemical Technology     Open Access   (Followers: 5)
ChemInform     Hybrid Journal   (Followers: 4)
Chemistry & Industry     Hybrid Journal   (Followers: 2)
Chemistry Central Journal     Open Access   (Followers: 5)
Chemistry of Materials     Full-text available via subscription   (Followers: 149)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
ChemSusChem     Hybrid Journal   (Followers: 5)
Chinese Chemical Letters     Full-text available via subscription   (Followers: 3)
Chinese Journal of Chemical Engineering     Full-text available via subscription   (Followers: 3)
Chinese Journal of Chemical Physics     Hybrid Journal   (Followers: 1)
Coke and Chemistry     Hybrid Journal   (Followers: 1)
Coloration Technology     Hybrid Journal  
Computational Biology and Chemistry     Hybrid Journal   (Followers: 9)
Computer Aided Chemical Engineering     Full-text available via subscription   (Followers: 1)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
CORROSION     Full-text available via subscription   (Followers: 19)
Corrosion Engineering, Science and Technology     Hybrid Journal   (Followers: 35)
Corrosion Reviews     Hybrid Journal   (Followers: 3)
Crystal Research and Technology     Hybrid Journal   (Followers: 5)
Current Opinion in Chemical Engineering     Open Access   (Followers: 4)
Education for Chemical Engineers     Hybrid Journal   (Followers: 4)
Eksergi     Open Access  
Emerging Trends in Chemical Engineering     Full-text available via subscription  
European Polymer Journal     Hybrid Journal   (Followers: 40)
Fibers and Polymers     Full-text available via subscription   (Followers: 4)
Fluorescent Materials     Open Access   (Followers: 1)
Focusing on Modern Food Industry     Open Access   (Followers: 2)
Frontiers of Chemical Science and Engineering     Hybrid Journal   (Followers: 1)
Gels     Open Access  
Geochemistry International     Hybrid Journal   (Followers: 2)
Handbook of Powder Technology     Full-text available via subscription   (Followers: 3)
Heat Exchangers     Open Access   (Followers: 1)
High Performance Polymers     Hybrid Journal  
Hungarian Journal of Industry and Chemistry     Open Access  
Indian Chemical Engineer     Hybrid Journal   (Followers: 4)
Indian Journal of Chemical Technology (IJCT)     Open Access   (Followers: 9)
Industrial & Engineering Chemistry     Full-text available via subscription   (Followers: 9)
Industrial & Engineering Chemistry Research     Full-text available via subscription   (Followers: 20)
Industrial Chemistry Library     Full-text available via subscription   (Followers: 3)
Industrial Gases     Open Access  
Info Chimie Magazine     Full-text available via subscription   (Followers: 3)
International Journal of Chemical and Petroleum Sciences     Open Access   (Followers: 2)
International Journal of Chemical Engineering     Open Access   (Followers: 6)
International Journal of Chemical Reactor Engineering     Hybrid Journal   (Followers: 2)
International Journal of Chemical Technology     Open Access   (Followers: 5)
International Journal of Chemoinformatics and Chemical Engineering     Full-text available via subscription   (Followers: 2)
International Journal of Food Science     Open Access   (Followers: 3)
International Journal of Industrial Chemistry     Open Access  
International Journal of Polymeric Materials     Hybrid Journal   (Followers: 5)
International Journal of Science and Engineering     Open Access   (Followers: 4)
International Journal of Waste Resources     Open Access   (Followers: 3)
Journal of Chemical Engineering & Process Technology     Open Access   (Followers: 4)
Journal of Applied Crystallography     Hybrid Journal   (Followers: 5)
Journal of Applied Electrochemistry     Hybrid Journal   (Followers: 10)
Journal of Applied Polymer Science     Hybrid Journal   (Followers: 103)
Journal of Biomaterials Science, Polymer Edition     Hybrid Journal   (Followers: 9)
Journal of Bioprocess Engineering and Biorefinery     Full-text available via subscription  
Journal of Chemical & Engineering Data     Full-text available via subscription   (Followers: 10)
Journal of Chemical and Biological Interfaces     Full-text available via subscription   (Followers: 1)
Journal of Chemical Ecology     Hybrid Journal   (Followers: 6)
Journal of Chemical Engineering     Open Access   (Followers: 6)
Journal of Chemical Engineering and Materials Science     Open Access   (Followers: 2)
Journal of Chemical Science and Technology     Open Access   (Followers: 4)
Journal of Chemical Sciences     Partially Free   (Followers: 17)
Journal of Chemical Technology & Biotechnology     Hybrid Journal   (Followers: 10)
Journal of Chemical Theory and Computation     Full-text available via subscription   (Followers: 15)
Journal of CO2 Utilization     Hybrid Journal   (Followers: 2)
Journal of Coatings     Open Access   (Followers: 4)
Journal of Crystallization Process and Technology     Open Access   (Followers: 6)
Journal of Environmental Chemical Engineering     Hybrid Journal   (Followers: 3)
Journal of Food Measurement and Characterization     Hybrid Journal  
Journal of Food Processing & Technology     Open Access  
Journal of Fuel Chemistry and Technology     Full-text available via subscription   (Followers: 4)
Journal of Fuels     Open Access  
Journal of Geochemical Exploration     Hybrid Journal  
Journal of Industrial and Engineering Chemistry     Hybrid Journal   (Followers: 1)
Journal of Information Display     Hybrid Journal  
Journal of Inorganic and Organometallic Polymers and Materials     Partially Free   (Followers: 6)
Journal of Modern Chemistry & Chemical Technology     Full-text available via subscription   (Followers: 2)
Journal of Molecular Catalysis A: Chemical     Hybrid Journal   (Followers: 5)
Journal of Non-Crystalline Solids     Hybrid Journal   (Followers: 7)
Journal of Organic Semiconductors     Open Access   (Followers: 4)
Journal of Physics and Chemistry of Solids     Hybrid Journal   (Followers: 5)
Journal of Polymer and Biopolymer Physics Chemistry     Open Access   (Followers: 4)
Journal of Polymer Engineering     Hybrid Journal   (Followers: 8)
Journal of Polymer Research     Hybrid Journal   (Followers: 6)
Journal of Polymer Science Part C : Polymer Letters     Hybrid Journal   (Followers: 5)
Journal of Polymers     Open Access   (Followers: 2)
Journal of Polymers and the Environment     Hybrid Journal   (Followers: 1)
Journal of Powder Technology     Open Access   (Followers: 1)
Journal of Pure and Applied Chemistry Research     Open Access   (Followers: 1)
Journal of the American Chemical Society     Full-text available via subscription   (Followers: 237)
Journal of the Bangladesh Chemical Society     Open Access  
Journal of the Brazilian Chemical Society     Open Access   (Followers: 2)
Journal of The Institution of Engineers (India) : Series E     Hybrid Journal   (Followers: 1)
Journal of the Pakistan Institute of Chemical Engineers     Open Access   (Followers: 1)
Journal of the Taiwan Institute of Chemical Engineers     Hybrid Journal   (Followers: 2)
Journal of Water Chemistry and Technology     Hybrid Journal   (Followers: 8)
Jurnal Inovasi Pendidikan Kimia     Open Access  
Jurnal Reaktor     Open Access  
Jurnal Teknologi Dan Industri Pangan     Open Access   (Followers: 1)
Korean Journal of Chemical Engineering     Hybrid Journal   (Followers: 3)
Main Group Metal Chemistry     Hybrid Journal   (Followers: 1)
Materials Chemistry and Physics     Full-text available via subscription   (Followers: 14)
Materials Science and Applied Chemistry     Open Access  
Materials Sciences and Applied Chemistry     Full-text available via subscription  
Molecular Imprinting     Open Access  
MRS Communications     Hybrid Journal  
Nanocontainers     Open Access  
Nanofabrication     Open Access  
Noise Control Engineering Journal     Full-text available via subscription   (Followers: 2)
Ochrona Srodowiska i Zasobów Naturalnych : Environmental Protection and Natural Resources     Open Access  
Petroleum Chemistry     Hybrid Journal   (Followers: 1)
Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B     Full-text available via subscription   (Followers: 3)
Plasma Processes and Polymers     Hybrid Journal  
Plasmas and Polymers     Hybrid Journal  
Polymer     Hybrid Journal   (Followers: 100)
Polymer Bulletin     Hybrid Journal   (Followers: 7)
Polymer Composites     Hybrid Journal   (Followers: 13)
Powder Technology     Hybrid Journal   (Followers: 12)
Recyclable Catalysis     Open Access   (Followers: 1)
Research on Chemical Intermediates     Hybrid Journal  
Reviews in Chemical Engineering     Hybrid Journal   (Followers: 5)
Revista Cubana de Química     Open Access  
Revista ION     Open Access  
Revista Mexicana de Ingeniería Química     Open Access  
Rubber Chemistry and Technology     Full-text available via subscription   (Followers: 2)
Russian Chemical Bulletin     Hybrid Journal   (Followers: 2)
Russian Journal of Applied Chemistry     Hybrid Journal   (Followers: 1)
Science and Engineering of Composite Materials     Hybrid Journal   (Followers: 54)
Solid Fuel Chemistry     Hybrid Journal  
South African Journal of Chemical Engineering     Open Access   (Followers: 2)
South African Journal of Chemistry     Open Access   (Followers: 2)
Surface Engineering and Applied Electrochemistry     Hybrid Journal   (Followers: 5)
Sustainable Chemical Processes     Open Access   (Followers: 1)
Synthesis Lectures on Chemical Engineering and Biochemical Engineering     Full-text available via subscription  
The Canadian Journal of Chemical Engineering     Hybrid Journal   (Followers: 3)
The Chemical Record     Hybrid Journal   (Followers: 1)
Theoretical Foundations of Chemical Engineering     Hybrid Journal   (Followers: 2)
Transition Metal Chemistry     Hybrid Journal   (Followers: 2)
Transylvanian Review of Systematical and Ecological Research     Open Access  
Visegrad Journal on Bioeconomy and Sustainable Development     Open Access   (Followers: 1)
Zeitschrift für Naturforschung B : A Journal of Chemical Sciences     Open Access   (Followers: 1)


Journal Cover Chemical Engineering Science
  [SJR: 1.178]   [H-I: 114]   [18 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0009-2509
   Published by Elsevier Homepage  [2969 journals]
  • Numerical analysis of gasification and emission characteristics of a
           two-stage entrained flow gasifier
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Bo Zhang, Zhuyin Ren, Shaoping Shi, Shu Yan, Fang Fang
      A two-stage dry-feed oxygen-blown entrained flow gasifier of HNCERI (Huaneng Clean Energy Research Institute) has been numerically studied through an integrated CFD-ROM approach, in which computational fluid dynamics (CFD) simulation is employed to investigate the detailed flow, temperature and composition fields, as well as to provide necessary information for the construction of reactor network-based reduced order model (ROM). A 10-step gasification chemistry together with an eight-step pollutant formation model optimized for the HNCERI gasifier have been constructed to investigate the gasification characteristics and emission of NO x , NH3, HCN, COS, SO2 etc. Computational results show that a ROM consisting of two perfectly stirred reactors and one plug flow reactor can accurately reproduce the available gasification and emission industrial data in minutes on a PC and thus is suitable to integrate with process flowsheet simulation. Heterogeneous reactions are found to dominate the gasification process in the second stage of the gasifier. The CO/H2 distribution in product syngas is determined by the water gas shift reaction at the downstream of the second stage where it reaches equilibrium. A sensitivity analysis shows that the coal and oxygen feed rates have pronounced effects on gasification characteristics while the effects of the steam feed rate and pressure are minimal. In addition, the decrease in the ratio of the coal feed rate of the second stage to the total coal feed rate may further increase the gasification efficiency, the effective gas production rate and carbon conversion with slight decrease in the temperature within the gasifier.

      PubDate: 2016-07-24T10:46:20Z
  • Microparticle trajectories in a high-throughput channel for contact-free
           fractionation by dielectrophoresis
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Yan Wang, Fei Du, Georg R. Pesch, Jan Köser, Michael Baune, Jorg Thöming
      Continuous, contact-free fractionation of sensitive microparticles at high throughput is a challenge. For this purpose, we developed a sheath flow assisted dielectrophoretic (DEP) field-flow separator with a tailored arrangement of cylindrical interdigitated electrodes (cIDE) and observed size-dependent trajectories of dispersed particles. Using a voltage input of 200Veff at a frequency of 200kHz, polystyrene particles (45, 25, and 11µm in diameter) levitated to different heights along the channel length due to a negative DEP force. Experimental observations agree well with simulated particle trajectories that were obtained by a modified Lagrangian particle tracking model in combination with Laplace's and Navier–Stokes equations. By exploiting the size-dependent levitation height difference the desired particle size fraction can be collected at a specific channel length. The required channel length of the proposed cIDE separator increases with decreasing particle size to be separated. The quality of theoretical fractionation, which we quantify by resolution, improves strongly with reduced collector width, reduced volume flow rate and increased voltage input. The sensitivity of these dependencies increases with decreasing particle size. We calculated a theoretical throughput of up to 47mLmin−1 when trading-off design and operation parameters, allowing for contact-free fractionation of sensitive microparticles with negligible shear stress.

      PubDate: 2016-07-24T10:46:20Z
  • Structural characteristics of adlayer in heterogeneous catalysis
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Fei Sun, Wen Lai Huang, Jinghai Li
      This paper explores the adsorbate distributions in the adlayer for a model system of heterogeneous catalysis, A+B→AB. Relevant kinetic mechanisms are revealed in terms of Shannon entropy via kinetic Monte Carlo (KMC) simulations. It is reckoned that reactions account for the clustering of the adsorbates, whereas diffusion and desorption tend to homogenize the adsorbate distribution besides adsorption, and diffusion exhibits a relatively stronger role. The clustering tendency seems to compete with the homogenizing one, showing alternate dominance in microscale space and time. The compromise between these two tendencies was reflected as the extremal tendencies at the mesoscale and the macroscale. However, such extremal tendencies can be maximization or minimization of Shannon entropy, depending on the choice of the initial state, implying the insufficiency of a single extremal function of Shannon entropy.
      Graphical abstract image

      PubDate: 2016-07-24T10:46:20Z
  • Modelling agglomeration and deposition of gas hydrates in industrial
           pipelines with combined CFD-PBM technique
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Boris V. Balakin, Simon Lo, Pawel Kosinski, Alex C. Hoffmann
      Hydrates of light hydrocarbons are frequently formed during the subsea petroleum production. These crystalline ice-like solids may accumulate at concentrations sensitive from the flow assurance point of view, increasing the overall pumping costs and imposing sufficient risk of the pipe blockage. Modern trend in the assessment of hydrate-related risks is the development of numerical models of multiphase flows laden by hydrates. The present paper describes a computational fluid dynamic (CFD) model capable to simulate turbulent slurry of oil, water and gas hydrates. The population balance technique (PBM) coupled with CFD enables to predict such details of the process as the formation of hydrate phase, agglomeration of formed solids and granular interactions within the hydrate phase. The simulation results, validated with experimental data in terms of the slurry rheology, highlight flow patterns for a pipe system typical in oil industry. The model is in addition compared to the hydrate kinetics model from Colorado School of Mines (CSMHyK).

      PubDate: 2016-07-24T10:46:20Z
  • CFD optimization of feedstock injection angle in a FCC riser
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Sheng Chen, Yiping Fan, Zihan Yan, Wei Wang, Xinhua Liu, Chunxi Lu
      Feedstock injection zone is a key section for fluid catalytic cracking (FCC) riser reactor. In conventional design of commercial FCC risers, the injection angle of the feedstock is 30° upward with the riser axis, which is found to easily cause nonuniform oil-catalyst contact and severe back-mixing in the feedstock injection zone. In this work, the effect of feedstock injection angle is investigated by performing 3-D simulations with seven injection configurations including three inclined upward, one horizontally and three inclined downward. The two-fluid model (TFM) and the energy-minimization multi-scale (EMMS) drag is combined in simulations. Comparison with experimental data is conducted in terms of the profiles of solids and feed volume fractions. Several variables including the backflow ratio, the radial nonuniformity index and the mean residence time of feed, are further introduced to quantify the hydrodynamic dependence of flow and mixing on the injection settings. It is found that the downward injection schemes are better to realize uniform mixing and matching between catalysts and feed than the upward injection schemes. A 30° downward injection angle is desired to improve the distributions of catalysts and feed, reduce the catalyst-feed contacting time and eliminate the effect of secondary flow on severe back-mixing near the riser wall.
      Graphical abstract image

      PubDate: 2016-07-24T10:46:20Z
  • Multi-objective operation optimization of ethylene cracking furnace based
           on AMOPSO algorithm
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Zhiqiang Geng, Zun Wang, Qunxiong Zhu, Yongming Han
      The objective of this article is to research and design a multi-objective operation optimization strategy and comprehensive evaluation method of solutions, to efficiently solve the multi-objective operation optimization problem of ethylene cracking furnace. An adaptive multi-objective particle swarm optimization (AMOPSO) algorithm is proposed and developed based on dynamic analytic hierarchy process (AHP). The algorithm adopts fuzzy consistent matrix to select the global best solution, which ensures the right direction of particle evolution. Furthermore, the evolution state is measured to adjust the weight and learning coefficients adaptively. The proposed method is applied to the operation optimization of ethylene cracking furnace. Two cases are studied including the fixed cracking cycle with four objectives and the non-fixed cracking cycle with five objectives. According to the preferences, decision makers can select the appropriate operation optimization conditions from alternative Pareto optimal solutions by the results of fuzzy evaluation. A feasible solution is provided for the multi-objective operation optimization of ethylene cracking furnace.
      Graphical abstract image

      PubDate: 2016-07-24T10:46:20Z
  • Influence of the heating method on the particle characteristics of copper
           oxide powders synthesized from copper nitrate aqueous solutions
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Tomoomi Segawa, Tomonori Fukasawa, An-Ni Huang, Yoshikazu Yamada, Masahiro Suzuki, Kunihiro Fukui
      The influence of the heating method and rate on the morphology of CuO powders synthesized from Cu(NO3)2·3H2O aqueous solutions by denitration was investigated. The median diameter of the obtained powder was found to decrease as the heating rate increased, independent of the heating method. The microwave heating (MW) method remarkably reduced the particle size and enhanced the irregularity and disorder of the shape and surface of the particles, which were found to be more widely distributed. In contrast, the microwave hybrid heating (MHH) method (i.e., a combined usage of microwave and external heating) yielded the most spherical particles with the smoothest surface. It was also found that this heating method sharpened the particle size distribution and had higher energy efficiency than the MW method. Numerical simulations also indicated a difference in the energy efficiency between these two methods. The simulations also revealed that the MHH method could heat the whole reactor more uniformly with a lower microwave output. Moreover, the morphological difference of the powders obtained by these heating methods can be potentially explained by the difference in the simulated bulk temperature distribution and the intensity of the formed hot spot in the CuO particles caused by microwave irradiation.
      Graphical abstract image

      PubDate: 2016-07-24T10:46:20Z
  • Three-dimensional simulation of micrometer-sized droplet impact and
           penetration into the powder bed
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Hua Tan
      In recent years, various drop-on-demand inkjet technologies capable of precisely delivering micron-sized droplets have been adopted in a few novel powder-based 3D printing processes. The droplet-powder interaction is an important step in these 3D printing technologies. In this paper, we propose a direct numerical simulation method to study the micron-sized droplets impacting on the powder bed. Since the powder particle size in our study is comparable to that of impacting droplets, the powder bed is modeled with a large number of rigid solid spheres fixed in their positions during the droplet impact. A set of important dimensionless parameters and scaling arguments is presented to elucidate the underlying physics involved in the micron-sized droplets impacting on powder. The Cartesian grid based volume-of-fluid method is used to track the immiscible liquid and air interface during the droplet-powder interaction. A contact angle model is proposed to include the wetting effect of the liquid agent on powder particles. The proposed numerical methods are implemented in an open-source code Gerris. Two numerical tests relevant to our study are conducted to validate the modified simulation code. Finally, we carry out simulations of a micrometer-sized droplet impacting on the powder bed with three different impact velocities. For low impact velocity, the droplet can even gain the momentum in the early stage due to strong capillary forces at contact lines compared to inertial force. The large impact velocity results in a wider spread and deeper penetration, however the liquid distribution inside the powder bed can be segmented because of high impact energy. The numerical method proposed in our study can be used to design suitable droplet-powder systems as well as determine optimal printing conditions in the inkjet-assisted powder-based 3D printing technologies.

      PubDate: 2016-07-24T10:46:20Z
  • On fiber behavior in turbulent vertical channel flow
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Niranjan Reddy Challabotla, Lihao Zhao, Helge I. Andersson
      In the present work, the dynamic behavior of inertial fibers suspended in a turbulent vertical channel flow has been investigated. The three-dimensional turbulent flow field was obtained from the Navier–Stokes equations by means of direct numerical simulation in an Eulerian reference frame. The fibers were modeled as prolate spheroidal particles in a Lagrangian frame and characterized by their inertia and shape. The translation and rotation of the individual fibers were governed by viscous forces and torques as well as by gravity and buoyancy according to Newton’s laws of motion. The test matrix comprised four different Stokes numbers (inertia) and three different aspect ratios (shape). The twelve different fiber types were suspended both in a downward and in an upward channel flow. Fiber orientation and velocity statistics were compared with channel flow results in absence of gravity. The results showed that gravity has a negligible effect for fibers with modest inertia, i.e. low Stokes numbers, whereas gravity turned out to have a major impact on the dynamics of highly inertial fibers. Irrespective of the bulk flow direction, a preferential alignment of the inertial fibers with the gravity force was found in the channel center where fibers have been known to orient randomly in absence of gravity. In the downward channel flow, the drift velocity of the fibers towards the walls was substantially higher for fibers than for spheres and also higher than when gravity was neglected. In the upward flow configuration, the modest drift velocity of inertial spheres was totally quenched for all fibers irrespective of shape. The suppressed drift velocity resulted in a more uniform fiber distribution throughout the channel as compared to the distinct near-wall accumulation in downward flow and in absence of gravity. This suggests that an upward flow configuration should be the preferred choice if a uniform fiber distribution is desired, as in a biomass combustion reactor.

      PubDate: 2016-07-24T10:46:20Z
  • The role of the Boudouard and water–gas shift reactions in the
           methanation of CO or CO2 over Ni/γ-Al2O3 catalyst
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Jin Yang Lim, James McGregor, Andrew J. Sederman, John S. Dennis
      The Boudouard and the water–gas shift reactions were studied at different temperatures between 453 and 490K over a Ni/γ-Al2O3 catalyst in a Carberry batch reactor using various mixtures of CO, H2 and CO2. The activity of the Boudouard reaction was found to be low, compared to the water–gas shift reaction, and diminished over time, suggesting that the temperature was too low for significant activity after an initiation period of CO adsorption. Furthermore, the rate of the Boudouard reaction has been reported to decrease in the presence of H2O and H2. The water–gas shift reaction was found to be the main reaction responsible for the production of CO2 in a mixture of CO, H2 and H2O in the batch reactor. The ratio of the total amount of CO consumed to the total amount of CO2 produced showed that the catalyst was also active towards hydrogenation, where the rate of the hydrogenation reaction was very much faster than the water–gas shift reaction. The resulting ratio of p H 2 to p CO was found to be extremely low, probably leading to the production of long-chain hydrocarbons. The stoichiometry of the overall reaction was such that for every mole of CO2 produced, 1.5 mol of CO was consumed in the batch reactor. Kinetic studies were performed in the batch reactor. An Eley-Rideal mechanism was found to provide a good agreement with the experimental results over a wide range of partial pressures of steam and CO.

      PubDate: 2016-07-24T10:46:20Z
  • CuO-Fe2O3-CeO2/HZSM-5 bifunctional catalyst hydrogenated CO2 for enhanced
           dimethyl ether synthesis
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Xinhui Zhou, Tongming Su, Yuexiu Jiang, Zuzeng Qin, Hongbing Ji, Zhanhu Guo
      A series of CuO-Fe2O3-CeO2 catalysts with various CeO2 doping were prepared via the homogeneous precipitation method, characterized and mechanically mixed with HZSM-5. Their feasibility and performance for the synthesis of dimethyl ether (DME) via CO2 hydrogenation in a one-step process were evaluated. The formed stable solid solution after the CuO-Fe2O3 catalyst modified with CeO2 promoted the CuO dispersion, reduced the CuO crystallite size, decreased the reduction temperature of highly dispersed CuO, modified the specific surface area of the CuO-Fe2O3-CeO2 catalyst, and improved the catalytic activity of the CuO-Fe2O3-CeO2 catalyst. The addition of CeO2 to CuO-Fe2O3 catalyst increased the amount of Lewis acid sites and Brønsted acid sites, and enhanced the acid intensity of the weak acid sites, which in turn promoted the catalytic performance of CO2 hydrogenation to DME. The optimal introduced amount of Ce in the catalyst was determined to be3.0 wt%. The CO2 conversion and DME selectivity were 20.9%, and 63.1%, respectively, when the CO2 hydrogenation to DME was carried out at 260°C, and 3.0MPa with a gaseous hourly space velocity of 1500mLgcat −1 h−1.
      Graphical abstract image

      PubDate: 2016-07-24T10:46:20Z
  • Influence of solids concentration on diffusion behavior in sewage sludge
           and its digestate
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Yuyao Zhang, Huan Li, Yingchao Cheng, Can Liu
      High-solids anaerobic digestion of sewage sludge is a promising technology, but blocked mass transfer is a key problem. However, the blockage process is difficult to quantify due to lack of direct evidence and data. In this study, a modified diffusion membrane cell was used to analyze the diffusion coefficients in high-solids sludge using iodide ions as a soluble tracer. The total solids (TS) concentration was verified to have a significant influence on the mass transfer in the sludge. The diffusion coefficients decreased sharply due to the decrease in free water when sludge TS concentration increased from 6% to 12%; the coefficients then decreased gradually, mainly by capillary diffusion, to a lower value when sludge TS increased further to 15%. Compared with the diffusion coefficient in water, the value in the diluted dewatered sludge at TS 14.92% decreased almost eightfold, while the value in the digested sludge at TS 15.21% decreased over 90 times. Furthermore, the diffusion coefficients in the digested sludge were an order of magnitude lower than in the diluted dewatered sludge at the same water content, because the digested sludge had smaller sized particles and less free water.

      PubDate: 2016-07-17T11:10:25Z
  • Electrochemical impedance spectroscopy for analyzing microstructure
           evolution of NaA zeolite membrane in acid water/ethanol solution
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Xianshu Cai, Yuting Zhang, Liangwei Yin, Dandan Ding, Wenheng Jing, Xuehong Gu
      NaA zeolite membrane exhibits high separation performance in dehydration of organics. However, the structural stability of NaA zeolite membrane is a critical issue for large-scale applications. In this study, electrochemical impedance spectroscopy (EIS) was first adopted to reveal the microstructure evolution of NaA zeolite membrane. Pervaporation separation of NaA zeolite membranes in acid water/ethanol solution was investigated for comparison. The permeation flux decreased initially and then increased while the separation selectivity declined continually. SEM, EDS and XRD characterizations showed structural degradation of NaA zeolite membrane layer in acid environments. Electrochemical impedance of NaA zeolite membrane was measured in acid solutions. The variation trend in the electrochemical impedance was found to agree well with that for separation performance caused by microstructure evolution. An equivalent circuit model was also constructed to evaluate electrical properties of the membrane system.
      Graphical abstract image

      PubDate: 2016-07-17T11:10:25Z
  • Butanol production by Clostridium acetobutylicum in a series of packed bed
           biofilm reactors
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): F. Raganati, A. Procentese, G. Olivieri, M.E. Russo, P. Gotz, P. Salatino, A. Marzocchella
      The continuous production of Acetone, n-Butanol and Ethanol (ABE) by immobilized cells of Clostridium acetobutylicum DSM 792 using glucose and lactose as carbon source is presented in this paper. The conversion process was successfully carried out for more than three months in 4 packed bed biofilm reactors (PBBRs) connected in series. The first PBBR of the series (fed with fresh medium) was kept under acidogenesis conditions and the three other PBBRs were kept under solventogenesis conditions. Each PBBR was a glass tube (4cm ID, 8cm high) with a 4 cm-bed of 3 mm-Tygon rings as carriers. The PBBR system was fed with 100g/L of lactose medium. The fermentation process was characterized in terms of metabolite production (butyric and acetic acids, acetone, butanol, and ethanol), sugar conversion and mass of biofilm. The overall dilution rate (DTOT) was varied between 0.15h−1 and 0.9h−1 to assess the PBBR system performance as a function of DTOT. The best PBBR system performance under optimized conditions was: butanol productivity 9.2g/Lh, butanol concentration 10.8g/L, acetone concentration 2.4g/L, ethanol concentration 1.8g/L, selectivity of butanol with respect to all solvents 72%w. To the authors’ knowledge, these butanol productivity and concentration values are the highest in the literature on lactose/(cheese whey) fermentation. An interpretation of the biofilm structure in the PBBR was put forward.

      PubDate: 2016-07-17T11:10:25Z
  • Effects of particle size distribution on drying characteristics in a drum
           by XDEM: A case study
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Mohammad Mohseni, Bernhard Peters
      The objective of this study is analysis of drying process of wet woody particles in a circulating cylinder including dynamics investigation of moving particles by eXtended Discrete Element Method (XDEM). In this approach, the particles are resolved as discrete phase coupled via heat, mass and momentum transfer to the surrounding gas phase. The drying of a spherical single particle is validated with experiments for different particle diameter and the temperature behavior during drying is investigated in addition to the moisture content and drying rate of the particle so that the comparisons show a good agreement meaning XDEM is a reliable tool to simulate drying process. The test case is a cylinder rotating with a constant angular velocity including a bed of moist wood particles. The main focus of this work is evaluating the effect of particle size distribution on drying rate and heat loss in the system. Furthermore, the influence of the inlet gas temperature and velocity on the particle bed mean temperature and moisture content is investigated. Eventually, the surface temperature distribution of particles in different instances during drying is visually demonstrated and the behavior of surface area on residence time is discussed.

      PubDate: 2016-07-17T11:10:25Z
  • Structure-transport relationships in disordered solids using integrated
           rate of gas sorption and mercury porosimetry
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Artjom Nepryahin, Elizabeth M. Holt, Rob S. Fletcher, Sean P. Rigby
      This work describes a new experimental approach that delivers novel information on structure-transport relationships in disordered porous pellets. Integrated rate of adsorption and mercury porosimetry experiments have been used to probe the relative importance of particular sub-sets of pores to mass transport rates within the network of two disordered porous solids. This was achieved by examining the relative rates of low pressure gas uptake into a network, both before, and after, a known set of pores was filled with frozen, entrapped mercury. For catalyst pellets, formed by tableting, it has been found that the compaction pressure affects the relative contribution to overall mass transport made by the subset of the largest pores. Computerised X-ray tomography (CXT) has been used to map the spatial distribution of entrapped mercury and revealed that the relative importance of the sub-sets of pores is related to their level of pervasiveness across the pellet, and whether they percolate to the centre of the pellet. It has been shown that a combination of integrated mercury porosimetry and gas sorption, together with CXT, can comprehensively reveal the impact of manufacturing process parameters on pellet structure and mass transport properties. Hence, the new method can be used in the design and optimisation of pellet manufacturing processes.
      Graphical abstract image

      PubDate: 2016-07-17T11:10:25Z
  • Ammoximation of cyclohexanone to cyclohexanone oxime using ammonium
           chloride as nitrogen source
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Yuanyuan Xu, Qiusheng Yang, Zhihui Li, Liya Gao, Dongsheng Zhang, Shufang Wang, Xinqiang Zhao, Yanji Wang
      A novel process was designed for synthesis of cyclohexanone oxime using ammonium chloride as nitrogen source. Various reaction parameters were optimized such as the amount of ammonium chloride, catalyst and H2O2, reaction temperature, reaction time. Under the suitable reaction conditions, nearly 100% of conversion of cyclohexanone and 100% selectivity of cyclohexanone oxime were obtained at ambient condition. The reaction mechanism was proposed by combining experiments with density functional theory calculations.
      Graphical abstract image

      PubDate: 2016-07-17T11:10:25Z
  • Influence of the carbon chain length of a sulfate-based surfactant on the
           formation of CO2, CH4 and CO2–CH4 gas hydrates
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Christophe Dicharry, Joseph Diaz, Jean-Philippe Torré, Marvin Ricaurte
      This study investigates how the length of the carbon chain of homologous surfactants affects the amount and growth rate of gas hydrates formed in quiescent CO2/CH4/water systems. The hydrate formation experiments were conducted using sodium alkyl sulfates with different carbon-chain lengths (C8, C10, C11, C12, C13, C14, C16 and C18), at a concentration of 10.4molm−3. The CO2:CH4 ratios investigated were 0:100, 25:75, 75:25, and 100:0. Hydrate formation was studied in a batch reactor at an initial subcooling of about 5K. It was observed to be efficient only for those surfactants that promote the formation of a water-wettable porous hydrate structure, which spreads over the inner sidewalls of the hydrate-formation cell. For the CO2:CH4 ratios of 0:100, 25:75, 75:25 and 100:0, hydrate formation was efficient for the surfactants with respectively 8 to 14, 11 to 13, 11 to 12, and 12 carbon atoms in their alkyl chain. Only the surfactant with 12 carbon atoms was found to promote and accelerate hydrate growth for all the gas-phase compositions tested. The much lesser surfactant effect on hydrate growth rate observed with the increase in the initial CO2 fraction in the gas phase is ascribed to a modification of the adsorption behavior of the surfactant molecules on the hydrate surface, which, as already suggested by Zhang et al. (2010), is probably due to competitive adsorption between the surfactant anions and bicarbonate.

      PubDate: 2016-07-17T11:10:25Z
  • Integration of simulated moving bed chromatography and enzymatic
           racemization for the production of single enantiomers
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Markus Fuereder, Christian Femmer, Giuseppe Storti, Sven Panke, Matthias Bechtold
      Integration of enantioseparation by simulated moving bed (SMB) and mild enzymatic racemization enables the production of single enantiomers from a racemic mixture in theoretically 100% yield and hence overcomes the 50% yield limitation of conventional SMB processes. We implemented such a process consisting of a Chirobiotic TAG column-SMB, an amino acid racemase-containing enzyme membrane reactor, and a nanofiltration unit for concentration of the distomer-enriched SMB raffinate prior to racemization on lab-scale for the production of enantiopure D-methionine. The integrated process scheme was operated continuously for over 30h without significant variations in product concentration and purity and with a yield of 93.5%, demonstrating the feasibility of this integrated process concept. Furthermore, a rational analysis of the integrated process on the basis of a short-cut model was conducted. The process model consists of a true moving bed equilibrium stage model to represent the SMB, a continuous stirred tank reactor model with reversible Michaelis–Menten kinetics to represent the enzyme membrane reactor, a nanofiltration model and feed node mass balances, and enabled the identification of optimal operating points (flow rate ratios, enzyme concentration) at a variety of process specifications and objectives. Optimal operating points were calculated for different cost distributions between the applied materials such as stationary phase, enzyme, solvent, and nanofiltration membrane. By assigning plausible pricing data and lifetimes to the respective materials, variable costs for the specific process considered in this work were estimated.

      PubDate: 2016-07-13T03:27:13Z
  • Local gas holdup simulation and validation of industrial-scale aerated
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Christian Witz, Daniel Treffer, Timo Hardiman, Johannes Khinast
      To date, the efficiency of industrial-size bioreactors has mainly been improved based on empirical knowledge. Computer simulation may help to understand the processes that occur inside the reactor and to develop new reactor designs. Euler-Lagrange simulations of the two-phase flow in large bioreactors, which could not be performed within a timeframe suitable for engineering purposes due to the limited computation resources, were made possible by the calculation power of graphic cards. The lattice Boltzmann method is well suited for parallelization which makes it ideal for calculating the fluid field inside a reactor driven by multiple Rushton turbines on graphic processing units. The bubble movements were captured via a Lagrangian approach by solving the Newton’s equations of motion. A two-way coupling between the disperse and continuous phases was applied. Break up and coalescence of the bubbles were modeled via stochastic algorithms using the approach rate of small turbulent eddies and the comparison of the contact time and film breakage time, respectively. To gather experimental data, a conductivity sensor was used to measure the local gas holdup. The rate and the duration of current drops were recorded to estimate the bubble size and the void fraction around the sensor’s tip position. The sensor was used in a 150l custom-built acrylic reactor. Several flow regimes with varying gas flow rates and stirrer speeds were investigated. The experimental results were in good agreement with the simulation data, especially at low stirring and low aeration rates. To prove the applicability of the code to large-scale problems, a 40m3 reactor was simulated.

      PubDate: 2016-07-13T03:27:13Z
  • Flame aerosol synthesis of WO3/CeO2 from aqueous solution: Two distinct
           pathways and structure design
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Shuhao Wang, Yun Huang
      Flame aerosol synthesis is a continuous one-step method to obtain metal oxides. However, production of uniform particle is considered an inherent challenge for flame aerosol synthesis from aqueous solution. It is necessary to fully understand the synthesis route and the essential governing factors to break through the barrier. A series of flames with different temperatures were employed to synthesize WO3, CeO2 and the WO3/CeO2 composite powders. Flame temperature and precursor concentration were investigated to determine the synthesis pathways from aqueous droplet to particle. Size distribution of the powders indicated that they were homogeneous (unimodal) micron particles at low temperature flame process, nanopowders at high temperature, and inhomogeneous (bimodal) particles in between. Two distinct pathways (droplet-particle and droplet-vapor-particle) were generalized from experiments and verified by size statistics. It was the competition between the temperature of flame and the vapor pressure of precursor solute that played an important role on selection of pathways. Based on the different response to temperature, the nanosized WO3/CeO2 mixture and nanoparticle-decorated WO3@CeO2 were designed. Furthermore, this generalized method was applicable for other tungsten oxide nanostructured catalysts, e.g. WO3@Al2O3, WO3@ZrO2.
      Graphical abstract image

      PubDate: 2016-07-09T03:14:51Z
  • Application of a new model based on oxygen balance to determine the oxygen
           uptake rate in mammalian cell chemostat cultures
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Yandi Rigual-González, Lucía Gómez, Jonathan Núñez, Mauricio Vergara, Alvaro Díaz-Barrera, Julio Berrios, Claudia Altamirano
      The application of dynamic methods for determining the oxygen uptake rate (OUR) in continuous mammalian cell cultures frequently ignores contributions to the oxygen balance such as the oxygen content in the culture medium inlet and outlet and the oxygen transfer between the culture and the headspace through the culture surface. We develop a mathematical model that allows OUR determination in mammalian cell chemostat cultures through a dynamic method, incorporating these neglected variables, as well as the application and validation of this model at two culture temperatures, 37°C and 33°C. The proposed model was compared with a model that only includes the OUR term (typical model). The standard error of the proposed model was less than that of the typical model, making the proposed model more accurate. The results showed that at 37°C, the results significantly differed depending on which model was used. At 33 and 37°C, the specific oxygen uptake rate (q O2) values obtained with the proposed model were within the range usually reported for mammalian cells. It was also shown that the OUR value was underestimated if the oxygen transfer through the headspace-medium interface was not considered under mild hypothermia conditions. The model could be applied for developing strategies based on OUR monitoring and controlling for recombinant protein production under conditions of mild hypothermia.

      PubDate: 2016-07-09T03:14:51Z
  • Unified Design of chromatographic processes with timed events: Separation
           of ternary mixtures
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Tuomo Sainio
      An important unifying property of single and multicolumn chromatographic processes, whether discontinuous or continuous, is that they are based on timed events. The Unified Design method was revised by defining three kinds of events (cut event, fixed-bed event, SMB event). Binary and multicomponent separations in various process configurations, from single column batch to complex multicolumn units, can readily be described as combinations of such events. New dimensionless parameters were introduced to describe these events, and their combinations were used as operating parameters for different processes. Transformations between physical and dimensionless operating parameters were introduced. Regions of feasible operating parameters for complete separation of ternary mixtures with linear isotherms were derived for batch chromatography and two SMB-type processes (Japan Organo, 3W−ISMB) using the equilibrium theory. It was shown that these can be visualized and overlaid on the Unified Design operating parameter plane, which enables their direct comparison. It was found that in many cases the complete separation regions of apparently very different process schemes are identical or exhibit strong similarities. This indicates that it should be possible to transfer the operating point from one process mode to another without affecting the product purity if column efficiency is very high.

      PubDate: 2016-07-09T03:14:51Z
  • Simulation and optimization of a 6-step dual-reflux VSA cycle for
           post-combustion CO2 capture
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Maninder Khurana, Shamsuzzaman Farooq
      The lowest energy consumption reported so far for CO2 capture from dry flue gas (CO2/N2=15/85) with 95% purity and 90% recovery is 148kWh/tonne of CO2 captured (Haghpanah et al., 2013b). The process is a 4-step VSA cycle comprising light product pressurization (LPP), high pressure adsorption (HPA), co-current blowdown (CoBn) and countercurrent evacuation (CnEv) on 13X zeolite, and the evacuation pressure (P L) is 0.03bar. The maximum productivity, although at a somewhat higher energy, is 0.6mol/m3 adsorbent. In this cycle, 95–90 purity-recovery is unachievable at P L above 0.04bar. In contrast, we propose a 6-step dual-reflux VSA cycle with LPP, HPA, heavy reflux (HR) using the product from the light reflux (LR) step, CoBn, CnEv and LR that can achieve 95–90% purity-recovery targets set by the U.S. Department of Energy without requiring deep vacuum. Optimum performances of the two cycles are compared for 13X Zeolite, the current industrial benchmark for CO2 capture, and UTSA-16, a promising MOF structure. Minimum energy and maximum productivity for the two cycles are presented as function of the P L for both the adsorbents. The optimum P L for both VSA cycles is found to be ~0.02atm with respect to both objectives. The 6-step cycle can deliver 95–90% purity-recovery of the captured CO2 up to a P L of 0.20atm (~0.2bar). The increase in energy consumption is modest up to P L of 0.1atm (~0.1bar). In the comparable P L range, the 6-step cycle also delivers significantly higher productivity than the 4-step cycle. Between UTSA-16 and 13X zeolite, the former performs at 19–24% lower energy and 51–75% higher productivity in the 4-step cycle, and 14–19% lower energy and 107–154% higher productivity in the 6-step cycle in the range of P L investigated.

      PubDate: 2016-07-09T03:14:51Z
  • Premixed combustion of methane–air mixture stabilized over porous
           medium: A 2D numerical study
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Valerio Giovannoni, Rajnish N. Sharma, Robert R. Raine
      The advancing development of small portable devices and miniaturization of electronic components such as smartphones, laptops, Global Positioning Systems (GPS), Unmanned Aerial Vehicles (UAVs) and sensors have led to an increasing demand for small scale power generators, such as the Ultra Micro Gas Turbine (UMGT). This study focuses on the two dimensional numerical investigation of premixed methane–air flames stabilized over a porous medium in a cylindrical combustion chamber which is a fundamental part of an UMGT. A reduced skeletal mechanism of methane combustion including 17 species and 73 reactions was employed for the simulations. The main objective of the present work is to investigate the effect of important parameters such as incoming mixture mass flow rate, equivalence ratio, reactants’ initial temperature, thermal conductivity and porosity of flame holder on the combustion process. Results show that combustion can be considerably affected by the flame holder, especially because under certain conditions it could lead to considerable heat losses and eventually flame quenching. Generally when the burning velocity is much higher than the incoming flow velocity, the flame lays on the surface of the porous medium and heat is lost through the flame holder causing a decrease in the flame temperature. On the other hand, when the flame is slightly lifted from the flame holder, heat is dispersed to the outer wall and through axial conduction the porous medium is heated up, allowing the mixture to increase its temperature before combustion. Finally the effect of the thermal conductivity and porosity of the porous medium are analysed, showing that the more insulating the flame holder is, the less heat losses occur.

      PubDate: 2016-07-09T03:14:51Z
  • Electrochemical reduction of CO2 to methanol over MWCNTs impregnated with
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): M. Irfan Malik, Zuhair Omar Malaibari, Muataz Atieh, Basim Abussaud
      This study evaluated the reduction of CO2 to methanol in the presence of effective and stable MWCNTs impregnated with Cu2O. A preliminary DFT study shows that the incorporation of Cu2O in MWCNTs improves the electronic properties of the electrocatalyst. The surface morphology and structural interaction between Cu2O and MWCNTs at different Cu2O loadings (10–50wt%) were characterized by SEM, TEM, EDX, XRD, BET, TGA, and Raman spectroscopy. Characterization results show that the Cu2O particles are incorporated at defect sites in the MWCNT matrix. However, higher lodgings (40 and 50wt%) result in the agglomeration of Cu2O particles and crystallite size growth. Electrochemical evaluation of the catalyst for CO2 reduction was conducted in a two-component polycarbonate electrochemical cell. Linear sweep voltammetry results show that the 30% Cu2O-MWCNTs catalyst gives the highest current density in the entire potential range, and a faradaic efficiency of 38% was achieved at −0.8V for the reduction of CO2 to methanol. The study shows that the impregnation of Cu2O on MWCNTs affects the structural and electronic properties of the electrode, which in turn improves both the activity and stability of the catalyst as confirmed by chronoamperometry.

      PubDate: 2016-07-09T03:14:51Z
  • DQMOM approach for poly-dispersed soot formation processes in a turbulent
           non-premixed ethylene/air flame
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Taehoon Kim, Yongmo Kim
      To realistically treat the poly-dispersed soot formation system, the Direct Quadrature Method of Moment (DQMOM) in conjunction with the transient flamelet approach was adopted to simulate a turbulent non-premixed C2H4/air flame. The population balance equation of the soot particle distribution was approximated using the multi-environment probability density function which consists of multiple weights and abscissas in the physical space. The transient flamelet model was employed to treat the turbulence-chemistry interactions and the two-equation soot model was used to account for the soot/gas chemistry coupling allowing mass and energy exchange. In the framework of the transient flamelet model, the physical soot model terms such as nucleation, surface growth, and oxidation for the population balance equation of soot particle distribution were closed. In terms of the mean temperature, soot volume fraction, primary soot particle number density, primary soot aggregate number density, mean number of primary particle per aggregate, mean radius of soot aggregate, and mean primary soot particle diameter, the predicted profiles agreed reasonably well with the experimental data.

      PubDate: 2016-07-09T03:14:51Z
  • Modeling and simulation of catalytic coal gasification in a pressurized
           jetting fluidized bed with embedded high-speed air jets
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Zihong Xia, Caixia Chen, Jicheng Bi, Kezhong Li, Yadan Jin
      A pressurized jetting fluidized bed catalytic coal gasification process has been developed in China. In order to avoid the hot spot at the bed bottom occurring in the conventional coal gasifier, and to reassign the oxygen distribution in the bed, a pair of embedded high-speed air jets was employed in addition to a bottom central jet. To examine the effects of the embedded air jets on the gas–solid hydrodynamics and the gasification process, a comprehensive model has been constructed by using the two-fluid method incorporated with the kinetic theory of granular flows. The established model was applied in the simulation of a 0.3t/d process development unit. The bed expansion was validated against the empirical correlation, and the bed pressure drop agreed with the value obtained by the Ergun equation. Some key jetting characteristics, including the jet height, the distributions of particle content, gas and solid velocities were presented. Comprehensive analyses of the simulation results showed that the embedded jets were able to split large bubbles, and improve the gas–solid contacts. A simulation for a conventional gasifier with a single bottom jet was performed, and the results were compared with the proposed embedded jets gasifier. For both schemes, a high temperature zone was predicted along the jet pathway due to a rapid combustion of char particles, the maximum temperature was, however, controlled well below the ash softening temperature for the embedded jets gasifier, mainly due to distributed oxygen supply. The carbon and steam conversions for the conventional gasifier were predicted lower than that of the embedded jets gasifier, indicating the embedded jets have enhanced the reactor performance due to the improvement of gas–solid mixing.

      PubDate: 2016-07-09T03:14:51Z
  • Model-based evaluation on simultaneous nitrate and arsenite removal in a
           membrane biofilm reactor
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Xueming Chen, Bing-Jie Ni
      Nitrate (NO3 −) and arsenite (As(III)) are two major contaminants in groundwater, which could cause significant risks to human wellbeing and ecological system. In this work, a single-stage membrane biofilm reactor (MBfR) coupling denitrifying anaerobic methane (CH4) oxidation (DAMO) and autotrophic As(III) oxidation processes was proposed for the first time to achieve the in-situ or ex-situ simultaneous removal of NO3 − and As(III) from groundwater. CH4 is supplied to the MBfR through gas-permeable membranes while NO3 − and As(III) are provided in the bulk liquid. A mathematical model was developed by integrating the well-established biokinetics of DAMO microorganisms with the kinetics of As(III)-oxidizing bacteria (AsOB). The key parameter values of AsOB were specifically estimated using the batch experimental data of an enriched pure AsOB culture in conjunction with thermodynamic state calculations. The maximum specific growth rate of AsOB ( μ AsOB ) and the yield coefficient for AsOB ( Y AsOB ) were determined to be 0.00161h−1 and 0.016g COD g−1 As, respectively. The modeling results demonstrated that both influent surface loading (or hydraulic retention time (HRT)) and CH4 surface loading played important roles in controlling the steady-state microbial community structure and thus significantly affected the system performance. The As(III)/NO3 − ratio between 0.1 and 2g As g−1 NO3 −-N in the influent would have no significant impact on the overall system performance despite the varying microbial composition in the biofilm. Through properly adjusting the influent surface loading (or HRT) and CH4 surface loading whilst maintaining a sufficient biofilm thickness at a suitable influent As(III)/NO3 − ratio, the maximum removal efficiencies of total nitrogen and As(III) could both reach above 95.0%, accompanied by a high CH4 utilization efficiency of up to 99.0%.

      PubDate: 2016-07-09T03:14:51Z
  • Filtered sub-grid constitutive models for fluidized gas-particle flows
           constructed from 3-D simulations
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Avik Sarkar, Fernando E. Milioli, Shailesh Ozarkar, Tingwen Li, Xin Sun, Sankaran Sundaresan
      The accuracy of fluidized-bed CFD predictions using the two-fluid model can be improved significantly, even when using coarse grids, by replacing the microscopic kinetic-theory-based closures with coarse-grained constitutive models. These coarse-grained constitutive relationships, called filtered models, account for the unresolved gas-particle structures (clusters and bubbles) via sub-grid corrections. Following the previous 2-D approaches of Igci et al. [AIChE J., 54(6), 1431–1448, 2008] and Milioli et al. [AIChE J., 59(9), 3265–3275, 2013], new closures for the filtered inter-phase drag and stresses in the gas and particle phases are constructed from highly-resolved 3-D simulations of gas-particle flows. These new closure relations are then validated through the bubbling-fluidized-bed challenge problem presented by National Energy Technology Laboratory and Particulate Solids Research Inc.
      Graphical abstract image

      PubDate: 2016-07-09T03:14:51Z
  • Engineering of the terpenoid pathway in Saccharomyces cerevisiae
           co-overproduces squalene and the non-terpenoid compound oleic acid
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Aamir Rasool, Genlin Zhang, Zhe Li, Chun Li
      The balanced and optimal expression of genes in an engineered pathway is a prerequisite for the overproduction of a natural compound in a customized strain. Hence, 13 new constitutive promoters were characterized and optimized for overexpressing genes in the squalene biosynthetic pathway (SB) and squalene overproduction in Saccharomyces cerevisiae. Subsequently, these newly characterized promoters were employed for overexpressing genes in the mevalonate pathway; as a result, 29.41-fold (100mg/L) more squalene was produced in the engineered strain (FOH-0) than in the wild-type strain (WS). Afterward, the entire squalene biosynthetic pathway was upregulated with the newly characterized promoters to engineer the FOH-2 strain, and it resulted in the production of 304.16mg/L of squalene after inhibition of squalene monooxygenase with terbinafine. The FOH-2 strain also overproduced 154.94mg/L oleic acid, and this was perhaps because of an indirect upregulation of the oleic acid biosynthetic pathway by an unknown regulatory mechanism. The production of ergosterol and biomass in the FOH-2 strain was also increased by up to 34mg/L and 13.5g DW/L, respectively, compared to the WS strain. Consequently, the overexpression of genes in the SB pathway increased the production of squalene, oleic acid, ergosterol and biomass by 89.46-, 4.66-, 3.37- and 2.25-fold, respectively, in the FOH-2 strain compared to the WS strain. The growth rate of the FOH-2 strain was also 1.3-fold higher than the WS strain. Finally, our study reports the enhanced coproduction of squalene, ergosterol, oleic acid and biomass in yeast due to the overexpression of genes in the SB pathway by newly characterized constitutive promoters. It also shows that ergosterol overproduction indirectly upregulates its complementary pathway.

      PubDate: 2016-07-09T03:14:51Z
  • Numerical modelling of flow and coupled mass and heat transfer in an
           adsorption process
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Dang Cheng, E.A.J.F. (Frank) Peters, J.A.M. (Hans) Kuipers
      In this paper, a detailed three dimensional mathematical formulation and a simplified one dimensional model for the numerical simulation of the flow and coupled heat and mass transport in a gas channel coated with adsorbing material are presented. In the three dimensional model, the velocity distribution of the gas flow is obtained by solving the momentum equation. The coupled heat and mass transport phenomena are locally described in both the gas channel and the adsorbent layer, and the concomitant adsorbate adsorption and desorption processes are taken into account. In the one dimensional model, the gas flow is assumed as a plug flow, and the heat and mass transfer across the solid-fluid interface is estimated by empirical transfer coefficients. A comparative study between the detailed three dimensional model and a simplified one dimensional model is carried out. Both model predictions are compared with experimental data available from literature. The heat and adsorbate concentration gradients observed in both radial and circumferential directions indicate that the detailed three dimensional model is desired. The time-dependent variations of temperature and heat flux distributions at the interface between the gas channel and the adsorbent layer justify the use of the more detailed three dimensional model. Three dimensional modelling is essential to obtain accurate predictions for cases where the solid side transport resistances are dominating.

      PubDate: 2016-06-30T03:02:56Z
  • Effects of harvesting cell density, medium depth and environmental factors
           on biomass and lipid productivities of Chlorella vulgaris grown in swine
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Hossein Amini, Lijun Wang, Abolghasem Shahbazi
      A regression model was developed to determine the growth rate of Chlorella vulgaris that is affected by the environmental factors of temperature, light intensity and pH value. The optimum environmental condition for growing C. vulgaris was experimentally determined at light intensity of 240 μ E m − 2 s − 1 , 24 ° C and pH of 7.4. At the optimum environmental condition, the growth rate of C. vulgaris in swine wastewater with 102mg N/l and 76mg P/l was 0.160g/l/day, compared to 0.191g/l/day for its growth on a modified Bold's medium with 100mg N/l and 53mg P/l. The regression model was further integrated with a light and heat transfer model to estimate the biomass productivity of C. vulgaris grown on the swine wastewater in an open raceway pond (ORP) with different medium depths and harvesting cell densities under the weather condition in North Carolina yearly around. At 20cm medium depth, the highest growth rate was 0.162g/l/day, which was obtained at 0.1g/l harvesting cell density, 24 ° C and 1350 μ E m − 2 s − 1 solar irradiance in August. If the medium depth increased to 30cm, the highest growth rate at 0.1g/l harvesting cell density was 0.156g/l/day, which was obtained at 23 ° C and 1500 μ E m − 2 s − 1 in June. If the harvesting cell density increased to 0.4g/l, the highest growth rate decreased significantly to 0.033 and 0.02g/l/day for 20cm and 30cm medium depths, respectively. At 0.1g/l harvesting cell density, the yearly algal productivity was 80 and 59t/ha at 30cm and 20cm medium depths, respectively. At the average 25% lipid content of C. vulgaris grown in swine wastewater, the highest lipid yield was 20 and 14.75t/ha/year at 30cm and 20cm medium depths, respectively.

      PubDate: 2016-06-30T03:02:56Z
  • A heuristic approach based on a single-temperature-peak design principle
           for simultaneous optimization of water and energy in fixed flowrate
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Wanni Xie, Yanlong Hou, Yuxin Wang, Jingtao Wang
      Methods of process integration could be classified in to two categories: the mathematical and conceptual method. The former is outstanding to solve the overall simultaneous synthesis problems, but sometimes, complex calculations will be needed. The conceptual method also could be employed to solve the problem about simultaneous optimization of water and energy but few of them could deal with the multiple contaminants problems. In this paper, a new heuristic approach is proposed to optimize simultaneously the water allocation and heat-exchange network (WAHEN) with both single and multiple contaminants in a fixed flowrate (FF) system. In order to build up this approach solidly, a principle of the single-temperature-peak design is proved through pinch analysis which discloses the interactions between water allocation network (WAN) and energy exchange network (HEN). When WAN only has a single-temperature-peak for each sub-stream, the heat recovery problem of this system could be a threshold problem requiring less energy. As a trade-off between water and energy consumption is established in this design principle, the water and energy consumption could be optimized at one step. Based on this single-temperature-peak design, a novel heuristic approach including two main designing steps, the design of WAN and HEN, is established. A graphical method is employed to design the original water allocation network to ensure it to be a single-temperature-peak type. Next, based on this WAN, WAHEN structures are further generated, which employs a method ensuring that the total energy consumption equals to the minimal value calculated by the first step. Graphical visualization is the advantage of this methodology, and it does not need complex mathematical calculations. Four literature examples are employed to check this new method. That the obtained optimization results are better than those of other works proves its effectivity and advantage. Currently, this paper mainly focuses on the water-reusing network, not the total network which will be investigated in our next work.

      PubDate: 2016-06-26T09:31:11Z
  • Modeling a production scale milk drying process: parameter estimation,
           uncertainty and sensitivity analysis
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): A. Ferrari, S. Gutiérrez, G. Sin
      A steady state model for a production scale milk drying process was built to help process understanding and optimization studies. It involves a spray chamber and also internal/external fluid beds. The model was subjected to a comprehensive statistical analysis for quality assurance using sensitivity analysis of inputs/parameters, and uncertainty analysis to estimate confidence intervals on parameters and model predictions (error propagation). Variance based sensitivity analysis (Sobol's method) was used to quantify the influence of inputs on the final powder moisture as the model output. Bayesian Inference using Markov Chain Monte Carlo sampling was used to quantify the uncertainty on the estimated parameters using available process data. In a full scale process the inputs with major range of variation are: moisture content at concentrate chamber feed (variation around 4%), and humidity at chamber inlet air (variation > 100%). The sensitivity analysis results suggest exploring improvements in the current control (Proportional Integral Derivative) for moisture content at concentrate chamber feed in order to reduce the output variance. It is also confirmed that humidity control at chamber inlet air stream would not be necessary because, despite its wide range of variation (air taken from outside), its impact on output variance is low. The uncertainty analysis results showed that confidence intervals obtained for parameters were reasonable, although some of them were found significantly correlated. For model applications, this means that model simulations should be performed using not only parameter values but also their correlation matrix by means of non-linear error propagation methods such as Monte Carlo techniques. The separate effects on model prediction uncertainties due to parameter estimation and measurement errors were studied. The results indicate that the error in measurements is the main responsible for the uncertainty in output predictions. Therefore using proper filtering of measurements, the comprehensively tested model is ready to support simulation based efforts for further process optimization.

      PubDate: 2016-06-26T09:31:11Z
  • Vacuum powder feeding and dispersion analysis for a solar thermochemical
           drop-tube reactor
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Majk Brkic, Erik Koepf, Ivo Alxneit, Anton Meier
      Ultrasonic vibratory and rotary valve particle feeders have been designed, constructed, and investigated for application to feeding reactant powder to a solar thermochemical drop-tube reactor. Zinc oxide and carbon particles are fed continuously to the drop-tube under vacuum pressures as low as 1mbar. The particles are probed in situ by laser transmission measurements with the aim to characterize particle residence time, axial and radial dispersion as a function of operating pressure. The ultrasonic feeder disperses particles well and can be operated at mass flow rates in the range of 57–288mgmin−1. The rotary valve feeder operates in the mass flow range of 3.46–41.96gmin−1 and exhibits reduced particle dispersion due to discrete pulsing mass flow created from the rotating valve. The time resolved transmission signals reflect characteristic changes under different experimental vacuum conditions. Particles traveling through the measurement zone at 1mbar exhibit residence and clearance times of 0.05s and 0.52s, respectively. At 960mbar, residence and clearance times are increased to as much as 0.16s and 3.98s, respectively. Particles falling at 1mbar show radial dispersion three times less than those falling under ambient pressure. A critical result of the functional characterization of powder feeding under vacuum is a potential reaction capacity limitation at low vacuum pressures due to short particle residence time and narrow axial dispersion.
      Graphical abstract image

      PubDate: 2016-06-26T09:31:11Z
  • Overproduction of squalene synergistically downregulates ethanol
           production in Saccharomyces cerevisiae
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Aamir Rasool, Muhammad Saad Ahmed, Chun Li
      Metabolic engineering strategies are often devised to redirect precursor flux in an engineered pathway. To develop a new strategy, the effect of overexpression of the squalene biosynthesis (SB) pathway and squalene overproduction on the ethanol production (EP) and post-squalene biosynthesis (PB) pathways was determined in Saccharomyces cerevisiae. Through overexpression of the HMG1, IDI1, ERG20 and ERG9 genes of the SB pathway, production of squalene increased 10-fold in the M1EG strain compared to the wild-type strain (WT) [(34mg/L), without terbinafine, an inhibitor of squalene monooxygenase, and 35.02-fold (119.08mg/L) with terbinafine]. However, due to overexpression of the SB pathway and squalene overproduction, production of ethanol and functionality of the EP and PB pathways were synergistically downregulated by 51.61%, 95.86% and 81.79%, respectively, in the M1EG strain compared to the WT strain. Overexpression of the entire SB pathway also enhanced production of squalene by 76.12-fold (304.49mg/L) and synergistically downregulated production of ethanol and functionality of the EP and PB pathways by 66.13%, 97.02% and 87.56% in the FOH-2 strain compared to the WT strain, respectively. The EP and PB pathways were strongly downregulated in the FOH-2 strain compared to the M1EG strain because the FOH-2 strain overexpresses the entire SB pathway and produces more squalene than the M1EG strain. These data suggest that overexpression of the SB pathway and squalene overproduction downregulate the EP and PB pathways in engineered strains. Therefore, we speculate that a cryptic regulation mechanism may downregulate these pathways, and characterization of such a mechanism may enable us to divert the precursor flux from the EP and PB pathways to the squalene biosynthesis pathway.

      PubDate: 2016-06-26T09:31:11Z
  • An integrated two-step Fr 13 synthesis - demonstrated with membrane
           fouling in combined ultrafiltration-osmotic distillation (UF-OD) for
           concentrated juice
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Wei Zou, Kenneth R. Davey
      Here we synthesize a two-step Fr 13 risk assessment (Davey et al., 2015; Davey, 2015) for the first time. We demonstrate it with vulnerability to fouling in an apparent steady-state global process of integrated cross-flow ultrafiltration and osmotic distillation (UF-OD) for concentration of fruit juice. Integrated two-step membrane processing of juices is becoming widespread as an alternative to thermal treatment. The aim was to advance the Fr 13 framework to investigate how naturally occurring, random fluctuations in apparent steady-state plant parameters can be transmitted and impact in progressively multi-step complex (i.e. integrated not ‘complicated’) processes. Membrane behavior is simulated using Monte Carlo (with Latin Hypercube) sampling of transmembrane pressure (∆P UF 1-1) and filtration time (t UF 1-1) with independent data for concentrating pomegranate juice (Punica granatum). Membranes fouling is defined as a permeate flux less than the operational design flux. Overall global failure of the integrated two-step UF-OD is defined as an unwanted OD flux (J OD 1-2<J OD 1-2, required plus 3% tolerance). Results show the Fr 13 method is applicable to an integrated two-step process. The integrated UF-OD is expected to be vulnerable to surprise fouling in 10.5% of all operations, over an extended time. Findings are used to assess re-design for reduced membrane vulnerability to fouling in second-tier studies. Results appear generalizable and could be applied to a range of integrated two-step processing. Outcomes will be of interest to risk analysts and manufacturers of membrane equipment. This work is part of an overall development and investigation of Fr 13 as a new quantitative risk assessment and equipment design tool.
      Graphical abstract image

      PubDate: 2016-06-26T09:31:11Z
  • Numerical simulation of 3D hollow-fiber vacuum membrane distillation by
           computational fluid dynamics
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Yonggang Zhang, Yuelian Peng, Shulan Ji, Shaobin Wang
      Computational fluid dynamics (CFD) was employed for modeling and simulation of the heat and mass transfer processes in hollow-fiber vacuum membrane distillation (VMD) under laminar flow conditions. A three-dimensional VMD model was first developed and validated by coupling the latent heat with the energy conservation equations and experimental data. Then it was used to analyze the effects of operating conditions and module dimensions on local temperatures, heat transfer coefficients, temperature polarization coefficients, heat and mass fluxes and total thermal efficiency in an operation of the feed flowing in the lumen of the fibers and the shell in vacuum. Thermal efficiency varied with feed temperature and feed velocity. Temperature polarization became more significant at high feed temperature and low feed velocity. Mass transfer was controlled by the heat transfer in the feed boundary. Local heat and mass fluxes decreased along the fiber length because of high local heat transfer coefficient in the inlet region and thin thermal boundary. More importantly, total thermal efficiency decreased with increasing module length, thus a short module was better used for high efficiency of VMD.

      PubDate: 2016-06-17T18:01:14Z
  • Development of a gas–solid drag law for clustered particles using
           particle-resolved direct numerical simulation
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Mohammad Mehrabadi, Eric Murphy, Shankar Subramaniam
      Particle-resolved direct numerical simulation (PR-DNS) is used to quantify the drag force on clustered particle configurations over the solid phase volume fraction range of 0.1 ≤ ϕ ≤ 0.35 and the mean slip Reynolds number range of 0.01 ≤ Re m ≤ 50 . The particle configurations and flow parameters correspond to gas–solid suspensions of Geldart A particles in which formation of clusters have been reported. In our PR-DNS, we use clustered particle configurations that match cluster statistics observed in experimental studies. To generate the particle configurations, we perform discrete element method (DEM) simulations of homogeneous cooling gas (HCG) systems with cohesive and inelastic particles in the absence interstitial fluid. Clustered particle sub-ensembles are then extracted from HCG simulations to match the statistics of cluster size distributions observed in experiments. These sub-ensembles are used for PR-DNS. It is found that the mean drag on clustered configurations decreases when compared to the drag laws for uniform particle configurations. The maximum drag reduction is observed in the configuration with low solid-phase volume fraction ϕ = 0.1 in Stokes flow, and is about 35 % . The drag reduction reduces with increase in both ϕ and Re m . A clustering metric is introduced to explain the behavior of the drag reduction with respect to solid-phase volume fraction. Also the behavior of the drag reduction with mean slip Reynolds number is related to the Brinkman screening length. PR-DNS results are then used to propose a clustered drag model for the range of flow parameters considered in this study. This clustered drag model provides a smooth transition between the uniform and clustered states by means of a weighting function with two model parameters.

      PubDate: 2016-06-17T18:01:14Z
  • The shape and behaviour of a granular bed in a rotating drum using
           Eulerian flow fields obtained from PEPT
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): A.J. Morrison, I. Govender, A.N. Mainza, D.J. Parker
      Non-invasive single-particle tracking techniques, such as positron emission particle tracking (PEPT), provide useful information about the behaviour of a representative particle moving in a bulk of similar particles in a rotating drum. The Lagrangian trajectories that they yield can be used to study, for example, particulate diffusion or granular interaction. However, often the Eulerian flow fields of the entire granular bed are more useful– they can be used to study segregation, for instance, or the evolution of the free surface of the bed. In this work, we present a technique for converting Lagrangian trajectories to Eulerian flow fields via a time-weighted residence time distribution (RTD) of the tracked particle. We then perform PEPT experiments on a mono-disperse bed of spherical particles in a cylindrical drum, rotated at various rates, and use the RTD procedure to obtain flow fields of the bed. We use these flow fields to investigate the effect of drum rotational speed on the shape and behaviour of a granular bed in a rotating drum, and the insights gained thereby to define a comprehensive set of surfaces– such as the bulk free surface– to divide the bed into regions of distinct granular behaviour. We further define scalar bed features– such as the centre of circulation of the bed– that can be used to quantitatively compare the behaviour of granular beds in rotating drums operated under various conditions.
      Graphical abstract image Highlights fx1

      PubDate: 2016-06-17T18:01:14Z
  • A new turbulence-induced theoretical breakage kernel in the context of the
           population balance equation
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Sandipan Kumar Das
      The current paper develops a new breakage kernel for use in the population balance equation. The study properly accounts for the direction of the relative velocity of the eddy and determines the size of the daughter bubble from the angle at which the eddy hits the parent bubble and its orientation at the point of impact. The breakup kernel considers both the capillary pressure of the parent bubble and the surface energy increase of the daughter bubbles in its formulation. The model predictions agree very well with the experimental data available in the literature. A parametric study of the breakage kernel further analyzes its behavior over a range of flow conditions. The parameterization also leads to a simplified breakage kernel.

      PubDate: 2016-06-17T18:01:14Z
  • The flow inside shaking flasks and its implication for mycelial cultures
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): C. Palacios-Morales, J.P. Aguayo-Vallejo, M.A. Trujillo-Roldán, R. Zenit, G. Ascanio, M.S. Córdova-Aguilar
      Several parameters such as mixing time, power consumption and deformation rates have been commonly reported in the literature for the hydrodynamic characterization of shaken flasks. In the present work, flow fields of orbital shaken flasks having different geometries have been experimentally obtained. Conventional, baffled and coiled flasks were tested at constant shaking speed of 150rpm at which the cultures are grown. Flow fields in terms of turbulence intensity and deformation rate were both determined by means of the Particle Image Velocimetry (PIV) technique. Velocity fields are strongly dependent on the flask geometry; in particular, the main flow is confined near the wall for the conventional geometry. In general, large velocity fluctuations are found in the whole flask for the baffled and coiled geometries, while the turbulence intensity is virtually zero at the center region for the conventional flask. The measurement of the average deformation rate indicates that flow obstacles, such as indentations and coiled springs, generate regions with high hydrodynamic stresses promoting the elongation and breakup of bubbles and biomass. Results from this study have been compared with previous studies finding good agreement for the same flask configurations at similar experimental conditions.
      Graphical abstract image Highlights fx1

      PubDate: 2016-06-17T18:01:14Z
  • Segregation and dispersion of binary solids in liquid fluidised beds: A
           CFD-DEM study
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Zhengbiao Peng, Jyeshtharaj B. Joshi, Behdad Moghtaderi, Md. Shakhaoath Khan, Geoffrey M. Evans, Elham Doroodchi
      Liquid fluidised beds often operate with particles of different sizes and densities, encountering partial or complete segregation of solid particles at certain operating conditions. In this study, the segregation and dispersion of binary particle species of the same size but different densities in liquid fluidised beds have been investigated based on the analysis of computational fluid dynamics – discrete element method (CFD-DEM) simulation results. The vertical fluid drag force acting on the particles was found to be responsible for the particle segregation. The mechanisms governing the particle dispersion strongly depended upon the solid–liquid two-phase flow regime, which transited from pseudo-homogeneous to heterogeneous when the superficial liquid velocity reached a certain value. In the homogeneous or pseudo-homogeneous flow regime (Re p≤40, ∈ L, ave≤0.74), particle collisions acted as the main mechanism that drove the dispersion of particles. However, after the system became heterogeneous, the magnitude of the vertical collision force decreased towards zero and correspondingly, the magnitude of the vertical fluid drag force was approaching that of the particle net weight force as the superficial liquid velocity increased. Therefore, in the heterogeneous flow regime (Re p>40, ∈ L, ave>0.74), the local turbulence of the fluid flow and particle collisions (if there were any) were found to be the main mechanisms that drove the dispersion of particles in all directions. The dispersion coefficient of individual particles varied significantly throughout the system in the heterogeneous flow regime. The simulation results reasonably agreed with the experimental data and the prediction results by existing correlations.
      Graphical abstract image

      PubDate: 2016-06-13T12:47:17Z
  • Fabrication and characterization of novel hollow fiber catalytic packing
           of PFSA–PES–ZrO2 (shell)–TiO2 (core) solid superacid via
           wet-spinning method
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Chen-Hao Ji, Shuang-Mei Xue, Zhen-Liang Xu, Xiao-Hua Ma
      In this work, a novel hollow fiber catalytic packing (HFCP) was fabricated of ZrO2 (shell)/TiO2 (core) (TZ) solid superacid nanoparticles, perfluorinated sulfonic acid resin (PFSA) and polyethersulfone (PES) via wet-spinning method. TZ was a homemade binary solid superacid nanoparticles with core–shell structure using superfine titania (5nm) as the core and mesoporous tetragonal phase zirconia as the shell. It was synthesized through the hydrolysis of zirconium oxychloride in the presence of titania nanoparticles and cetyltrimethylammonium bromide (CTAB) hexagonal crystals covered on the titania core and followed by calcination and acidification. HFCPs demonstrated well catalytic performance in the esterification test of ethanol and acetic acid due to the superacid sites on the surface of TZ and PFSA polymer chain. And the superacid sites on the PFSA polymer chain could be sufficiently exposed by the embedding of the nanoparticles. At the same time, HFCPs also showed ultrahigh recovery which was more than 99.5% in 6 runs because of the well integrality benefited from the wet-spinning method. The specific surface area (SSA) and pore size distribution were analyzed by N2 adsorption–desorption, the result showed that the SSA of HFCPs decreased with the increasing of the PFSA additive amount. The SSA of the HFCP with the best catalytic performance could be up to 90.60m2/g, in which the PFSA weight proportion was 13%. The XRD pattern and HRTEM image showed the HFCPs i.e. the zirconia shell of TZ formed uniform tetragonal phase. Other characterizations such as FT-IR, XPS, SEM and TEM were utilized to determine the chemical composition and morphology of the HFCPs and TZ, the results showed the novel catalytic packing was a suitable catalyst for the acid catalyzed reactions.
      Graphical abstract image

      PubDate: 2016-06-13T12:47:17Z
  • In-situ grown molybdenum sulfide on TiO2 for dye-sensitized solar
           photocatalytic hydrogen generation
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Ghodsieh Malekshoar, Ajay K. Ray
      Molybdenum sulfide was loaded on TiO2 by an in-situ solar photo-deposition method over a dye synthesized photocatalytic process using Eosin Y (EY) as a photo-sensitizer and tri-ethanolamine (TEOA) as an electron donor. (NH4)2MoS4 was also used as a precursor. The effect of molybdenum sulfide as a co-catalyst was investigated. The proposed noble-metal-free photocatalytic system exhibited high efficiency for H2 evolution. A systematic statistical design of experimental analysis was employed to explore the impact of various parameters and to subsequently optimize the photocatalytic hydrogen production. TEOA, EY and (NH4)2MoS4 concentrations as well as pH of the solution were selected as the four factors in the study, whereas the amount of hydrogen produced after 3h of solar irradiation was considered as the response. The possible mechanism for the in-situ solar photo-deposition method was also proposed.
      Graphical abstract image

      PubDate: 2016-06-13T12:47:17Z
  • Mixing performance evaluation of additive manufactured milli-scale
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Mihret Woldemariam, Roman Filimonov, Tuomas Purtonen, Joonas Sorvari, Tuomas Koiranen, Harri Eskelinen
      The mixing performance of three passive milli-scale reactors with different geometries was investigated at different Reynolds numbers. The effects of design and operating characteristics such as mixing channel shape and volume flow rate were investigated. The main objective of this work was to demonstrate a process design method that uses on Computational Fluid Dynamics (CFD) for modeling and Additive Manufacturing (AM) technology for manufacture. The reactors were designed and simulated using SolidWorks and Fluent 15.0 software, respectively. Manufacturing of the devices was performed with an EOS M-series AM system. Step response experiments with distilled Millipore water and sodium hydroxide solution provided time-dependent concentration profiles. Villermaux–Dushman reaction experiments were also conducted for additional verification of CFD results and for mixing efficiency evaluation of the different geometries. Time-dependent concentration data and reaction evaluation showed that the performance of the AM-manufactured reactors matched the CFD results reasonably well. The proposed design method allows the implementation of new and innovative solutions, especially in the process design phase, for industrial scale reactor technologies. In addition, rapid implementation is another advantage due to the virtual flow design and due to the fast manufacturing which uses the same geometric file formats.

      PubDate: 2016-06-13T12:47:17Z
  • Sensitivity of chemical-looping combustion to particle reaction kinetics
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): M.A. Schnellmann, S.A. Scott, G. Williams, J.S. Dennis
      A simple simulation for chemical-looping combustion (CLC) is discussed: two, coupled fluidised reactors with steady circulation of particles of oxygen carrier between them. In particular, the sensitivity of CLC to different particle kinetics is investigated. The results show that the system is relatively insensitive to different kinetics when the mean residence time of particles in each reactor is greater than the time taken for them to react completely.

      PubDate: 2016-06-13T12:47:17Z
  • PAT-based design of agrochemical co-crystallization processes: A
           case-study for the selective crystallization of 1:1 and 3:2 co-crystals of
           p-toluenesulfonamide/triphenylphosphine oxide
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): K.A. Powell, D.M. Croker, C.D. Rielly, Z.K. Nagy
      In this study, the selective crystallization and characterization of the stoichiometric forms of the p-toluenesulfonamide/triphenylphosphine oxide (p-TSA–TPPO) co-crystal system in acetonitrile (MeCN) is demonstrated using batch and semi-batch crystallizers. In the batch study, both 1:1 and 3:2 p-TSA–TPPO were successfully isolated as pure forms. However, process variability was observed in a few experimental runs. To address the batch process variability issue, a control strategy was implemented using temperature cycling, aided by in situ process analytical technologies (PAT) to convert from 3:2 to 1:1 p-TSA–TPPO. In the semi-batch co-crystallization studies, the two molecular co-formers, p-TSA and TPPO, were dissolved in MeCN and pumped separately to the crystallizer. Changing the flow rates of the respective active ingredients allowed control over the co-crystallization outcome, and presents as a promising opportunity for development of a continuous co-crystallization process.
      Graphical abstract image

      PubDate: 2016-06-13T12:47:17Z
  • Prediction of conductive heating time scales of particles in a rotary drum
    • Abstract: Publication date: 2 October 2016
      Source:Chemical Engineering Science, Volume 152
      Author(s): Heather N. Emady, Kellie V. Anderson, William G. Borghard, Fernando J. Muzzio, Benjamin J. Glasser, Alberto Cuitino
      Modeling conductive heat transfer from rotary drum walls to a particle bed via discrete element method simulations, three time scales were determined: 1) the characteristic heating time of the bed, τ; 2) the particle thermal time constant, τ p ; and 3) the contact time between a particle and the wall, τ c . Results fall onto a monotonic curve of τ/τ c vs. ϕ (τ p /τ c ), with three heating regimes. At low ϕ, conduction dominates, and the system heats quickly as a solid body. At high ϕ, granular convection dominates, and the bed heats slowly at a nearly uniform temperature. At intermediate ϕ, the system heats as a cool core with warmer outer layers. The results of this work have important implications for improving the design and operation of rotary drums (e.g., energy-intensive calcination processes). By calculating τp and τ c from material and operating parameters, the characteristic heating time, τ, can be predicted a priori.
      Graphical abstract image

      PubDate: 2016-06-13T12:47:17Z
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